Good advice. I definitely don't plan on doing any major modifications like that, I was just wondering if anyone has.

Personally I don't see the need to have a turbo/charged 128i or 135i in the GTA. Mostly due to Insurance cost & lack of fast public roads to take advantage of 135i power.
So enjoy the 128i for what it is - one of the last high revving Naturally Aspired BMW inline six cars